A retrospective study of idiopathic granulomatous mastitis diagnosis and clinical presentation

To the Editor: Granulomatous mastitis (GM) is a rare, poorly characterized inflammatory breast disease that frequently displays clinical and radiographic features of benign and malignant conditions, including infectious mastitis and inflammatory breast cancer.1Grover H. Grover S.B. Goyal P. et al.Clinical and imaging features of idiopathic granulomatous mastitis — the diagnostic challenges and a brief review.Clin Imaging. 2021; 69: 126-132https://doi.org/10.1016/j.clinimag.2020.06.022Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar Diagnostic challenges of GM are commonplace.2Pluguez-Turull C.W. Nanyes J.E. Quintero C.J. et al.Idiopathic granulomatous mastitis: manifestations at multimodality imaging and pitfalls.Radiographics. 2018; 38: 330-356https://doi.org/10.1148/rg.2018170095Crossref PubMed Scopus (36) Google Scholar,3Taylor G.B. Paviour S.D. Musaad S. Jones W.O. Holland D.J. A clinicopathological review of 34 cases of inflammatory breast disease showing an association between corynebacteria infection and granulomatous mastitis.Pathology. 2003; 35: 109-119Abstract Full Text PDF PubMed Google Scholar Several pathophysiologic mechanisms have been proposed for GM, however, the majority of cases are unexplained and ultimately termed idiopathic granulomatous mastitis (IGM).1Grover H. Grover S.B. Goyal P. et al.Clinical and imaging features of idiopathic granulomatous mastitis — the diagnostic challenges and a brief review.Clin Imaging. 2021; 69: 126-132https://doi.org/10.1016/j.clinimag.2020.06.022Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar,2Pluguez-Turull C.W. Nanyes J.E. Quintero C.J. et al.Idiopathic granulomatous mastitis: manifestations at multimodality imaging and pitfalls.Radiographics. 2018; 38: 330-356https://doi.org/10.1148/rg.2018170095Crossref PubMed Scopus (36) Google Scholar Recently, a large case series of 32 patients with IGM has been published.4Steuer A.B. Stern M.J. Cobos G. et al.Clinical characteristics and medical management of idiopathic granulomatous mastitis.JAMA Dermatol. 2020; 156: 460-464https://doi.org/10.1001/jamadermatol.2019.4516Crossref PubMed Scopus (10) Google Scholar In this retrospective study, we present our experience with 31 patients with IGM, describing epidemiologic, diagnostic, and clinical characteristics of the disease. The study was approved by the institutional review board of Massachusetts General Hospital. We selected patients with suspected GM referred and seen in our combined rheumatology-dermatology clinic to rule out autoimmune disease between 2012 and 2020 using International Classification of Diseases version 10 code N61.2 in the Epic (Epic Systems) electronic medical record and clinic schedules. The patients were seen by either a dermatologist with a rheumatologist or by a dermatologist alone, depending on scheduling availability. Demographics, clinical presentation, and relevant laboratory test, imaging, and biopsy results were extracted from chart review. Recommended workup was similar between specialists. Patients were assigned a diagnosis of IGM once other causes of mastitis were ruled out through laboratory workup and histopathologic analysis. Thirty-one patients, mean (SD) age 37.4 (7.7) years, were included in this study. None had concurrent autoimmune diseases. Additional demographic and clinical characteristics are summarized in Table I. Consistent with prior reports, the majority of patients were diagnosed less than 5 years after their last breast feeding and/or pregnancy.4Steuer A.B. Stern M.J. Cobos G. et al.Clinical characteristics and medical management of idiopathic granulomatous mastitis.JAMA Dermatol. 2020; 156: 460-464https://doi.org/10.1001/jamadermatol.2019.4516Crossref PubMed Scopus (10) Google Scholar Nearly half (n = 15; 48.4%) had unilateral, predominately left-sided disease; 3 patients (9.7%) had initially unilateral then bilateral involvement; and 3 (9.7%) had bilateral breast involvement at baseline. Twenty-seven (81.1%) experienced pain, 21 (67.7%) had at least 1 palpable nodule, 18 (58.1%) had clinically detectable skin erythema, and 14 (45.2%) developed induration of the involved breast(s) (Fig 1). The majority were of non-White race, including Black, Hispanic, and Asian.Table IDemographic information, clinical characteristics, and reproductive historyCharacteristicNo. (%)All patients31 (100)Age, mean (SD)[range]37.4 (7.7) [22-64]Race (ethnicity) White13 (42.0) Black2 (6.5) Hispanic9 (29.0) Asian5 (16.1) American Indian or Alaskan Native1 (3.2) Not recorded1 (3.2)Pattern of disease UnilateralRight breast10 (32.2)Left breast15 (48.4) Bilateral3 (9.7) Unilateral to bilateral3 (9.7)Clinical symptoms Nodule21 (67.7) Abscess10 (32.3) Ulceration4 (12.9) Nipple inversion3 (9.7) Pain27 (81.1) Erythema18 (58.1) Induration14 (45.2)Other findings Nipple discharge2 (6.5) Draining tracts2 (6.5) Tenderness4 (12.9)Lymphadenopathy6 (19.4)Time since most recent delivery <5 years23 (74.2) >5 years5 (16.1) Nulliparous1 (3.2) Pregnant2 (6.5)Times since most recent breastfeeding <5 years25 (80.6) >5 years4 (12.9) Nulliparous1 (3.2) Never breastfed1 (3.2)History of known trauma2 (6.5) Open table in a new tab Diagnostic tests included ultrasound (100%), mammography (64.5%), and breast biopsy (96.7%) (Table II). Breast biopsy showed a cystic neutrophilic pattern for the majority of patients (26; 83.9%) (Fig 2). Consistent with the literature, an association with Corynebacterium spp. was found, with breast fluid culture/smear positive for Corynebacterium spp. in 9 (of 26) tested cases.5Wu J.M. Turashvili G. Cystic neutrophilic granulomatous mastitis: an update.J Clin Pathol. 2020; 73: 445-453https://doi.org/10.1136/jclinpath-2019-206180Crossref PubMed Scopus (16) Google Scholar Of note, 2 patients were found to have elevated prolactin levels, and 2 patients had resolution of disease upon cessation of antidepressant medication. Furthermore, all patients previously failed antibiotic treatments prior to referral to our clinic.Table IIDiagnostic and laboratory testsAll patientsNo. (%)Breast ultrasound31 (100)Mammogram20 (64.5)∗Of 20, 1 result was unavailable.Chest x-ray Normal17 (54.8) Abnormal2 (6.5) Not done8 (25.8) Results not released4 (12.9)Bloodwork Elevated prolactin level2 (6.5) Positive TB test2 (6.5)Tissue culture for mycobacteria, fungi, and bacteria Positive (corynebacteria)3 (9.7) Negative11 (35.5) Not done17 (54.8)Breast biopsy pathology results Cystic neutrophilic pattern26 (83.9) Other pattern (eg, acute and chronic mastitis)3 (9.7) Not done1 (3.2) Results not available1 (3.2)Fluid culture/smear Positive corynebacteria9 (29.0) Negative corynebacteria17 (54.8) Not done5 (16.1)TB, Tuberculosis.∗ Of 20, 1 result was unavailable. Open table in a new tab TB, Tuberculosis. In contrast to Steuer et al,4Steuer A.B. Stern M.J. Cobos G. et al.Clinical characteristics and medical management of idiopathic granulomatous mastitis.JAMA Dermatol. 2020; 156: 460-464https://doi.org/10.1001/jamadermatol.2019.4516Crossref PubMed Scopus (10) Google Scholar our cohort did not show a predominance of Hispanic patients and the clinic presentation was slightly different, with fewer patients in our cohort experiencing nipple inversion (9.7% vs 44%) and draining tracts (6.5% vs 25%), respectively. All patients previously failed antibiotic treatments prior to referral to our clinic, which points to a more recalcitrant GM disease in our cohort. In this study, we aim to add to the current knowledge of the clinical presentations and diagnosis of IGM. A rare disease, increased consideration in working differentials and timely identification of IGM are critically important. None disclosed.